Your Pet's Best Friend

Food Allergy

So, we've been treating our itchy pet for allergic itching with a variety of approaches, but he is still itching.  How can this be?

It could be that, despite our skin scrapings, cultures and other in-office tests, we missed something and it's really not an allergy.  We may need to do a skin biopsy (cutting out a tiny piece of affected skin and sending it to a specialist who can look at every cell under the microscope and tell us what we are dealing with...we hope).  Often we have multiple underlying problems and we have to treat them all. If the patient is fifty percent better, we did something good.  BUT, we've still got to find the other fifty percent.  For instance, it's very common for dogs who traumatize their skin to develop secondary yeast infections.  Most yeast infections are just secondary opportunists, but once they are there you have to treat them if you want the patient to get well.

You already thought of that, you say?  You say that the biopsy shows nothing but the changes associated with allergic skin disease and this pet is still having major itchy problems despite all your good treatments?  Alas, I fear this means that we are dealing with a food allergy, particularly if the problem is not seasonal, but year round.

Dogs and cats with food allergy generally don't have diarrhea, just as pets with inhalant allergies generally don't have "hay fever" symptoms.  When these animals have allergic reactions, it is the skin that is affected.  You rolled in it, you breathed it, you ate it -- your skin breaks out.   Well, if it's the same kind of reaction, why isn't the food allergy getting better on the medicine?

If you were allergic to some plant, and you needed to take antihistamines, chances are that you would not go find a pile of that plant and rub it all over your body and stuff it up your nose.  Even though you yourself are not a scientist, it seems to you that putting your body into that much of what you're allergic to would be a bad idea.  Good thinking.  If you have a food allergy, the situation is similar.  YOU'RE EATING IT!  It's smeared all over your insides.  Your intestinal lining has so many microscopic nooks and crannies that it has way more surface area than the outside of your body.  The food allergy patient has such a heavy stimulation of his allergic reaction that the medicines frequently don't do much.  So whaddayagonnado?

The only way to diagnose a food allergy is with a dietary elimination trial.  The allergy testing methods that we use to identify molds and pollens and so forth will sure give you reactions on dietary ingredients, but they just aren't meaningful. Those tests may help you select a new diet for the patient if you prove he has a food allergy, but they cannot diagnose a food allergy.  Perfectly normal dogs and cats will react all over the place on those tests.

Contrary to what most folks think, the offending foodstuff won't be something new in the diet. The pet has to have been eating it for six months or more to become sensitized and develop an allergy to it.  Also, it isn't going to be just one brand of pet food.  It's going to be an ingredient (or two), like chicken, beef, corn, soybean, wheat, or some preservative or who knows what.  You can't just switch to a different food on the shelf.  For the dietary elimination trial, the pet will eat a diet composed of ingredients that are entirely new to him, and NOTHING else.  These can be home-cooked, or there are commercially prepared diets made of venison and green pea, duck and potato, kangaroo and oats, and other weird stuff.

A dietary elimination trial is the simplest thing in the world, in theory.  You stop eating this, you start eating that. Nothing to it.  In practice, however, things are more complicated.  When you start the special diet, you can't have treats, you can't have table food, you can't eat what the kids drop on the floor, the other pet's food, flavored heartworm preventive, rubber erasers... NOTHING but the special new diet.  Not only that, most pets take four to six weeks (and some longer) for all the old food to completely wash out of every little intestinal hidey-hole.  Try that with three pets and two little kids in the house.

If you think this post is way too long (and it is) imagine me giving this lecture (and the last two posts, as well) to three itchy patients a day.  Now you know why there aren't many veterinary dermatologists.

Scratch it till it's a bloody sore.

When my son got chiggers at camp, he asked his mom what to do about the itching.  She suggested the traditional remedies of Benadryl cream, Chigarid, or clear nail polish.  He didn't care for those alternatives, so I facetiously suggested that he "scratch them till they are bloody sores".  He gave me a quizzical look and walked off. Two days later, he informed me that he had indeed scratched the chiggers till they were bloody sores.  "How did that work?"  Not very well. "Better listen to your mother next time."

Dogs and cats with allergies have itchy skin as their most common problem.  When they itch all over, they scratch all over, sometimes until they get "bloody sores".  At this point they've exhausted their repertoire and have no alternate plan.  Despite the fact that they're still itchy, self-trauma is all they can do about it.  It's not surprising that the people who love them would like to try a different approach.

So, having determined that you don't have mange mites (by skin scrapings), or fungus (by culture), or yeast (impression smears), or fleas (careful combing under bright lights), and having taken a careful history and thorough physical examination (since skin problems are often the only visible part of whole body problems), we come to the conclusion that your pet is an allergy sufferer.  Whaddayagonnado about it?

I'll discuss the most common approaches to allergy treatment. If you're into "alternative medicine", I highly recommend Dr. Ava Frick.  She is the best, and not far way, in Union, Missouri. 

Since the allergy is a malfunction of the immune system (see yesterday's post), we can suppress the immune system with some form of cortisone (there are lots of synthetic drugs in this category).  This relieves inflammation and stops the body's over-reaction to the allergens (pollen, mold, house-dust, etc.). Unfortunately, it also affects your adrenal glands, your liver, your carbohydrate metabolism, your mood, your appetite, your urine output, and a lot of other stuff.  This means that it may work great to shut down your allergic reaction, but you can't eat it like popcorn.   High doses are pretty safe for short periods of time, but if your allergy is year-round instead of seasonal, high doses are not going to be safe.  Low doses given every two or three days are pretty safe for most (but not all) individuals.  We manage a lot of dogs this way.  It's very inexpensive and for many it is effective and the side-effects are liveable.

A newer approach to suppressing the immune system is cyclosporine (trade name is Atopica).  This drug does not have the side-effects of the cortisone derivatives.  It works really well for most patients.  Unfortunately, it is hideously expensive: think ten dollars a day for a forty-pound Boxer. Yow!  I've treated several dogs with it, but mostly very small dogs.

Antihistamines don't suppress or prevent the allergic reactions.  When you have an allergic reaction, histamine and other chemicals are released (and make you miserable).  The antihistamines are drugs that have effects that are the opposite of the allergic chemical mediators.  If the allergic chemicals are making the blood vessels open up someplace, the antihistamins are closing them down.  Instead of preventing messes, we try to clean up messes.  In people, this works pretty well.  In some people it works great!  In most animals, it works lousy.  Eighty percent of pets receive absolutely no benefit from antihistamines.  Of the twenty percent that do benefit, it's hard to predict which drug will work.  Benadryl might help a dog, while Atarax does nothing for him.  You try three or four before you quit.  Some of the best ones for people help NO dogs.  Sometimes the antihistamines just make the pet too sleepy to scratch.  He still itches, but it's too much trouble to move that leg.

Hyposensitization therapy is great when it works.  You test the pet to see what it is allergic to (and the bad allergy sufferers usually turn up with a dozen or so culprits).  Based on the test results, the allergy lab mixes up a sterile bottle of allergens. You get a little medicine vial with tiny amounts of sterilized mold, pollen, house-dust, and so forth.   We inject this under the patient's skin, starting with practically nothing, and gradually building up to a pretty good dose over a period of several weeks.  After a few months, you're just giving one shot every two to three weeks. When this works, the pet builds up a tolerance to these things and his immune system quits being so crazy.  When someone says they are getting "allergy shots", this is what they should be talking about (as opposed to long-acting cortisone shots, which are rather unpredictable, and usually not the best choice).

Allergies are things you manage, not things you cure.  But, hey, what if none of the above seem to be working?  Stay tuned...

Allergies are defense malfunctions.

It's not the heat, it's the stupidity.  That is, it's the stupidity of the body's defense system that results in allergies.  You've got this great and amazing array of mechanisms that protect your body from foreign invaders.  When some harmful germ or poisonous molecule (i.e. a really tiny thing that is bad for you) enters the body, it gets noticed.  It's not "self" and it doesn't belong and it's damaging things.  The damaged body cells release their dying breaths (so to speak: the biochemical equivalent of "Aaagh! They got me!").  These tiny chemical death cries bring the cavalry to the rescue to kill and clean up those baddies.  This is generally a good thing.

Of course, you also take in a lot of things that are not "self" that are also not harmful.  You just pass them through, or spit them out, or breath them back out again.  Did you ever look at a sunbeam coming in through the bedroom window and see all those bazillions of dust motes floating in the air?  And then hold your breath trying not to inhale any of that stuff?  And then give up, knowing that you've been inhaling that stuff all your life and you're going to keep doing it and not even noticing it?  Man, I try to look at sunbeams from a discrete distance so I don't suffocate on that stuff.

Most bodies can tell the difference between the harmful stuff and the sunbeam floaters.  Allergy sufferers, on the other hand, have some stupidity in their defenses (which we scientists call the  immune system).  These people and animals have immune systems that go nuts, over-reacting to stuff that's harmless.  Their defenses dump histamine and other chemicals that make them miserable -- runny eyes and nose and itching in people, while dogs and cats mostly have itchy skin.  It's not the pollen or the mold or the pieces of cricket nose-hair -- it's the over-reaction of the immune system.  The non-allergic individual stands right beside the sufferer, inhaling the same junk and feeling perfectly fine.

This makes for a tricky situation in trying to help these individuals.  Their body defenses have gone nuts, over-reacting, making them miserable.  Obviously, we're going to have to shut the defenses down to get any relief. But wait:  if we shut down the body defenses, the baddies can come in and run wild.  Dang! We're between a rock and a hard place now, ain't we?  Kind of reminds you of having to sacrifice your personal freedoms to be protected from terrorists.  No free lunch, is there?

What's worse is that the really bad allergy sufferers just keep developing new sensitivities.  Last year it was house-dust, ragweed, bread-mold, wool and hippopotamus dander.  This year we've added oak pollen, bermuda grass, penicillin and chicken salad.  You thought we'd just do some allergy testing and move away from whatever we're allergic to.  Alas, the really miserable patients usually have so many allergies that getting away from it all is not a workable option.

So, if your pet is a mass of self-induced scabs, or soon will be (you've just purchased an English Bulldog, Chinese Shar-pei, or some other genetically lucky individual), what ARE your options?

Stay tuned.